Process of making propellent powder



RATION OF DELAWARE.

0F WILMINGTON, DELAWARE, ASSIGNOR TO ANY, OF WILMINGTON, DELAWARE, A CORPO- PROGESS OF MAKING PROPELLENT POWDER.

No Drawing.

To all whom it may concern:

Be it known that I, RICHARD GEORGE WooDBRIDGE, Jr., a citizen of the United States, and a resident of Wilmington, in the county of New Castle and State of Delaware, have invented a certain new and useful Process of Making Propellent Powders, of which the following is a specification.

This invention relates to the production of nitrocellulose .powders of the progressive type, and comprises treating nitrocellulose powder grains with a deterrent material at an elevated temperature for a sufiicient length of time to cause substantial impregnat10n of said grains by the deterrent material. I

Improvements in processes of manufacturing progressive propellent powders have been described by me in Patents 1312463 and 1313459. According to the processes set forth in said patents thorough impregnationof nitrocellulose grains with a deterrent material was brought about by subjecting a mixture of the two materials to a prolonged treatment with hot water. in this manner gave much results than powder made by processes known in the prior art, such as the process of British Patent 15553 of 1898 to Frederick William Jones.

Jones was satisfied with obtaining a very superficial impregnation of the surface of the powder grains such aswould result from applying to the powder grains and surface coating-material, sufiicient heat to melt the latter. That in fact Jones made no attempt to secure complete impregnation of the powder grains is made clear in the description of his process set forth in the above mentioned patent; thus, for instance, in lines 10-27 page 5 he saysWhen using dinitrotoluene for this purpose, I first crush it to an impalpable powder. I then add it in Powders made better ballistic the powdered form to a charge of the gun-' powder in the drum. The proportion of dinitrotoluene added will be considerably greater than the proportion eventually taken up by the gun-powder, and may amount to as much as say, 5 per cent. I then drum the mixture for a period of time, perhaps 8 hours, more or less, which'sufiices to cause the grains to take up so much of the 'dinitrotoluene as is desired. I then remove the charge from the drum and sift it in order to Specification of Letters Patent.

Application filed March 14, 1921.

Patented Nov. 8, 1921. Serial No. 452,263.

separate the coated gunpowder from the residue of dinitrotoluene. I then take the coated powder and expose it in a suitable oven to a temperature of about 70 C. At this temperature the dinitrotoluene will melt, but being already evenly distributed over the grain, it does not, when brought into the molten condition, penetrate the grain owing to the viscous nature of the solid solvents and the small amount of nitrocellulose dissolved. The dinitrotoluene remains where it has been placed and the only effect of its being brought to the molten condition is that it becomes strongly adherent to the grain forming a non-explosive shell. In all cases, I prefer to glaze the coated grains with graphite to make them smooth and easy to load with.

A slower burning powder is in fact obtained by the Jones process just quoted, but such powder lacks the advantageous ballistic properties which characterize the powders made according to the above mentioned Patents Nos. 1312463 and 1313459.

In a further investigation of this subject to ascertain whether or not it was possible to improve the ballistics of a powder made substantially in accordance with the directions of the Jones patent, I caused .a large number of samples of such powder to be maintained for different periods of time, ranging from '15 minutes to 96 hours, at a temperature just sufficient to melt the deterrent material (a temperature of 70 0. when the deterrent was dinitrotoluene). Some remarkable results were obtained from this series of tests. The samples heated for various periods up to two hours showed practically no effect from this treatment, but samples heated for substantially more than two hours were found to have decidedly improved ballistic properties. The extent of the improvement in powders heated for more than two hours is indicated by the decrease in the pressure generated as compared with that generated by powderheated for less than 2 hours, the weights of charges in the different cases being such as to impart to the bullets substantially equal velocities; this decrease in pressure amounted to more than 2000 pounds per square inch.

The tests above mentioned may be described in greater detail as follows:

Smokeless powder was treated with about 5% of its weight of dinitrotoluene exactly in accordance with the directions contained in J oness British Patent 15553/98 i. e., drumming the mixture of powder and dinitrotoluene for a period of 8 hours, more or less, and then heating the powder thus coated in an oven at C.; but instead of heating only until the coating became molten, the heating was prolonged to the extent hereinafter indicated. The samples of the powder removed after 15 minutes, 1 hour, and two hours, respectively, of heating at 7 0 C., cooled and glazed with graphite, showed little or no improvement in ballistics except giving a slower burning powder requiring a higher weight of charge to give the same velocity with relatively no increase in pressure. point, I give the following ballistic results obtained in the U. S. 30/06 rifle using a 150- grain bullet:

1 Mean in- .Time we arsemg at O C (grains). 5??? per sq.in.).

none E 40. 5 2617 43320 15min. 42.0 2013 43000 1 hour 1 42. a 2616 44180 i 2hours 43.2 2043 43700 i 1 Weight Velocity Mean presg 'g 362% charge at 78 ft. sure (lbs.

g (grains). per 5. persq.in.).

The above-described experiments showed clearly that no improvement in ballistic results was obtainable in surface coating this particular type of base grain when the dinitrotoluene was left on the surface of the grain as an exterior coat-ing, and that a definite heat treatment at 70 C. was necessary in order to secure that impregnation of the surface ,of the powder by the dinitrotoluene which would result in giving a powder of improved ballistics. In describing the duration of the heat treatment it may therefore besaid, in general, that the heating should be continued until the deterrent material with increasing rapidity.

To illustrate this no longer exists on the surface of the powder grains as a distinct layer. treatment has been continued for the proper length of time the deterrent is found concentrated near the surface of the powder grains, but it has penetrated into the same for a considerable depth so that in the burning of the powder the successively exposed surfaces contain less and less of the deterrent, thus causing the combustion to proceed Such powders give a lower temperature in the gun, tending to reduce the erosion and flash produced and allow the attainment of a high velocity without undue increase in the pressure.

The process is applicable to the various kinds of small arms and cannon powders.

In the above description of the new process I have said that the powder, coated with, for example, dinitrotoluene, is heated for substantially more than 2 hours at a ternperature of about 70 C. It is desirable, especially when large batches of powder are being treated, to cause the increase in tem perature up to the final temperature of 70 C. to take place gradually. The tendency of the powder grains to stick together may be overcome by thoroughly mixing a small percentage of graphite therewith sometime before the temperature has reached the meltin point of the deterrent material.

I 01 the deterrent material I prefer to use 2.4-dinitrotoluene, but the other isomeric dinitrotoluenes or mixtures thereof may also be used, as well as the mononitrotoluenes. Instead of the foregoing explosive deterrents, I may use a mixture containing nonexplosive deterrents as, for example, dimethyldiphenylurea and phenylacetanilid. The deterrent material used, whether composed of a single substance or a mixture of substances, should preferably have a softening or melting point of such a value that impregnation of the grains will occur at a temperature of from about 70 to 80 C.

In the ordinary practice of the new process the powder, coated with from about 1 to 5% of deterrent material, is heated for the required length of time in the presence of air, but it is to be understood that the powder may alternatively be heated in the presence of any other inert medium as, for instance, carbon dioxid or nitrogen. The essential difference between the present process and the processes described in various prior patents in this particular art is that the powder, according to the present process, is given a prolonged heat treatment in the absence of any substantial amount of water in either the vapor or liquid form. In

other words the powder is heated while dry instead of while wet.

My invention is not limited to the details above set forth but may be modified in various ways within the scope of the appended After the heat 7 grains at a temperature of from about 70 to 80 C. in contact with a deterrent material capable of difi'using into said grains at sald temperature, and continuing said heating .10 until substantial impregnation of said grains with said deterrent material has occurred.

2. The rocess which comprises heating \substantiaily dry nitrocellulose powder ggains at a temperature of from about 70 to 8 O C. for substantially more than 2 hours in contact with a deterrent materialqcapable of difi'using into said grainsat said temperatures.

3. The process which comprises heating substantially dry nitrocellulose powder grains having a coating of a deterrent material amounting to from about. 1 to 5% of the weight of the nitrocellulose at a temperature of from about 70to 80 C. until the deterrent material no longer exists as a separate and distinct layer on said grains.

4. The process which comprises. heating substantially dry nitrocellulose powder grains having a coating of a dinitrotoluene amounting to from about 1 to 5% of the grains.

weight of the nitrocellulose at a tempera-' ture of from about'70 to 80 C. until the dinitrotoluene no longer exists as a separate and distinct layer on said grains.

5. The process which comprises heating,

while immersed in an inert gas, nitrocellulose powder grains having a coating of a dinitrotoluene for substantially more than 2 hours at a temperature of about 70 C. to cause the dinitrotoluene to diffuse into the body of the grains.

6. The process which comprises ,heating, while immersed in an inert gas, nitrocellulose powder grains mixed with graphite and having a coating of a'dinitrotoluene for substantially more than 2 hours at a temperature of about 70 C. to cause the dinitrotoluene to difiuse into the body of the grains. l

7. The process which comprises heating substantially dry nitrqeellulose powder grains having a coating of a dinitrotoluene amounting to about 5% of the nitrocellulose at a temperatureof about 70 C. for more than 2 hours and until substantially all of the dinitrotoluene has diflused into the In testimony whereof I afiix my signature.

RICHARD GEORGE WOODBRIDGE, .lr. 

